Improved bridge



grotten gistenl @stent @fitta EDWARD nAMiL'roN, or entorno, iLLiNois, AssieNon 'To HIMsnLr AND MATTHEW o. nare, or sinn PLAGE.

Letters'Pftten No. 78,202, dated May 26, i858; mttcdated M'ay 9, 1868. A

ntrnovsu BRIDGE.

TIO ALL WI-IOM IT HAY CONCER:

Be it known that I, EDWARD HAMILTON, of' the city ol' Chicago, in the county of' Cook,.and State of Illinois, have invented a new and useful Improvement-in the Construction of Bridges; and I do hereby declare thatA the following is a full, clear, and exact description of the saine, reference beinghad to the accompanying drawings, making a part of this specification, in which- Y Figure 1 is a section of chord, with. the front plate left oii',`sho,wing the bracing.

Figure 2 is an end view, showing roadway and'io'otpath or sidewalk.`

Figure 3 is a plan or top view, with aportion of the cap und superstructure for railway, a part being cut away to show the top of the chords and the bracing more distinctly.

Figure 4 is a perspective view of a portion of a draw-bridge.

Similar letters of reference in the severaliigures indicate corresponding parts in the drawings.

The nature of my invention consists in so constructing a bridge of iron, or wood and iron, as to combine,

with lightness, vgreat strength and durability. To do this I construct my chords with a ,combination of thin, butwide sheets oi' metal, iron, or steel, with wood or iron bracing between the sheets to prevent them from buig ing or buckling, so as to mar or destroy their power of resistanceto great pressure. These sheets of metal are put in edgeways, as shown in the drawings clearly at A. If wood bracing is used in the chords to prevent the bulging or buckling of the metallic sheets, it should be putin so close or thick as to prevent the same, and this can be done .so as to add lightness with economy oi' construction and great strength to the structure.

V A model bridge constructed by me for the purpose of testing this principle, about five feet long, and weighing thirty-sevenand a halt' pounds only, stood a test, under pressure, of over twenty tons.

It should also be stated that if wood is used in the chords, the top and bottom shouldbe covered with metal, to shut out the atmosphere, to prevent the wood from rotting, and add; durability to the structure, as it is awellknown fact that if the wood can' be kept from contact with the air and atmospheric changes, it will retain its soundness for a great length of time, and, in fact, become almost as durable as iron. i i ,o

The great object I havein view-is to so use the metal sheets insuch a manner edgeways as toobtui'n the greatest force of resistance to pressure which the metal is capable of standing, and at the same time secure the durability ofthe bridge, lightness of structure,'and economy in mode of construction.

To enable others skilled in the art. lwill now proceed to describe-my invention, and its .made of construction.

It will, however, be clearly understood from the foregoing, and the drawings, that the`principles evolved in my plan of construction could andn'iight be applied to many distinct forms of building. For draw-bridges and many other structures the plates should be widest in the centre, or so ast-o stand the greatest strain where it is mechanically shown to need or require it:

This principle may also be applied to streamers, girders, and timbers-of' great length, used to support heavy structures, as shown in the chords of the drawings. i i I A A are the sheets of metal used in the chords o r girders, suitably braced by means of wood or iron between the sheets of metal A, and firmlybeld together by means of bolts and straps. v This bracing of wood oriron on the inside, and between the sheets o` .metal A and the straps, G, on the outside, should be so constructed and formed as to prevent bulging or buckling ofthe sheets A. This feature, in combination with the angle-ironsat top andrbottom of the chord, is the one upon which I `predicate the importance and value of my invention, in connection, however, with the fact of multiplying the divisions in the chord to any extent desired to obtain the strength required for the structure.V I amnware that setting sheets or plates of iron on edge to form chords or bridge-girders is not new, but the lling and bracing, as clearly indicated by the drawings, tbgether with the division of the chordsarrd multiplicity of parts for adding strength to the structure, are distinctive features of noveltyand great utility. c i

B is the bracing between the sheets of metal A, and may be of wood, iron, or steel, and is required to be so Well or closely fitted in as to prevent buckling of the sheets.. C are brackets for the Support of foot-paths or sidewalks upon each side ofthe bridge,- and maybe made or constructed in any suitable manner for the purpose intended. D D are the angle-irons or plates of metal at top 4and bottom ofthe girder or chord. E are the cross or lateral timbers for bracing the chords, and forming the base for the superstructure or roadway. F are the cross-rods, .holding the same together crossways. F are theross-timb ers or angle-bracing to strengthen and support the structure. Gr are plates of metal on the outside, through which pass the bolts, fastening together the parts of the girder or chord. H are the bolts referred to. The straps G might be made angling, as shown at Gin red lines, to braceand strengthen the chord, and prevent buckling of the Voutside sheets.

It will be seen that the chords shown'in the drawings have three sheets of metal, one on each side and one .in theentre, forming the thickness of' the chord or-.girdein The great'strength of these plates, combined with bracing andvbolts, as shown, is fully demonstrated by tests, while its great simplicity, economy, and vlightness of structure can hardly fail to, commend'it to the favorable attention of builders.

It is well understood that the Wider a piece of timber is, (andthe fact holds goed in metals,) the more weight it will sustain. To prove which fact, take apiece of timber, twelve by twelve, inches, andsaw it into three-inch plank, and put the plank one on top of the other edgewise, and` keep them in position, and you have a much stronger beam than the timber was in its original state; and this idea, practically applied to the construction of bridges, beams, sills, girders, trusses, rafters, and all other means for sustaining great Weight, I regard as being the correct principle to adapt therefor.

It will be seen that I take thin sheets of iron or steel plate, of a suitablewidth and length for the service required. These plates are set up in the angle-iron at'the bottom of the chord or girder, the bracing is set up,

being ofthe proper thickness, and another sheet of metal isset up on the otherside;v another row of bracing is then applied, and then another sheet of metal, andso on'till the'required thickness and strehgth are obtained,

always commencing and` closing with the sheet of metal ou the'utside. The top is' then put on, and the chord securely bolted together ;v the bridge is then f 'orrrnedvv in any mode of, construction desired, the top and bottom plates thus protecting the inner bracing from the atmosphere. Thus it will be seen that I have no strain on the parts other than their own Weight, and I secure the most perfect and equal expansion and contraction of the metal without injuring or'straining the fibre or the parts. And this point is of great and acknowledged importance in the construction of bridges. The absence oi' this principle is a serions objection to bridges built on the truss plan. All timber in my bridge, when used at all, is perfectly secured from rot or decay by reason of the protection aiorded from the atmosphere as stated.A

From the foregoing description, and an examination of' the drawings, theyse, structure, and operation will be readily seen and understood.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent,is-

1. In combination with the sheets A of Vmetallic plates, placed edgewise to sustain the incumbent weight, I claim a system of cross-braces, B, to support the same, 'substantially in the manner set forth.

2'. In combination withithe metallic plates, disposed as set forth, and wooden -cross-braces for supporting the same, I claim plates for enclosing the spaces between the edges ofthe sheet, substantially as set forth.

Witness my hand lto my specification for improved mode of constructing bridges.

E. HAMILTON. Witnesses NATHAN YARNALL, EBER WOODRUFF. 

